Thermally cross-linked fluoropolymer

Abstract

Melt-fabricable thermoplastic fluoropolymer having pendant functional groups is thermally cross-linked in the presence of polyfunctional nucleophile.

What is claimed is:  
     
       1. A cross-linked fluoropolymer composition comprising a fluoropolymer which is thermoplastic, partially crystalline, and melt-fabricable prior to cross-linking and having pendant functional groups prior to cross-linking, said cross-linking of said fluoropolymer being carried out thermally in the presence of a polyamide cross-linking promoter intermixed with said fluoropolymer, said functional groups being capable of cross-linking by said promoter in the absence of catalyst to thereby obtain said cross-linking, wherein said fluoropolymer prior to cross-linking has a melt viscosity of 0.5×10 3  to 100×10 3  Pa·s. 
     
     
       2. A melt-fabricable fluoropolymer composition, comprising (a) partially crystalline thermoplastic fluoropolymer having pendant functional groups and (b) polyamide cross-linking promoter intermixed with said fluoropolymer, said functional groups being capable of cross-linking by said promoter in the absence of catalyst wherein said fluoropolymer has a melt viscosity of 0.5×10 3  to 100×10 3  Pa·s. 
     
     
       3. The composition of  claim 2  wherein no catalyst is present. 
     
     
       4. A melt-fabricable fluoropolymer composition consisting essentially of (a) partially crystalline thermoplastic fluoropolymer having pendant functional groups and (b) polyamide cross-linking promoter intermixed with said fluoropolymer, said functional groups being capable of cross-linking by said promoter wherein said fluoropolymer has a melt viscosity of 0.5×10 3  to 100×10 3  Pa·s. 
     
     
       5. The cross-linked fluoropolymer composition of  claim 1 , which is a blend of fluoropolymer which is free of said functional groups and fluoropolymer which has said functional groups. 
     
     
       6. The cross-linked fluoropolymer composition of  claim 1  wherein said fluoropolymer contains at least 35 wt % fluorine. 
     
     
       7. The composition of  claim 2  wherein said fluoropolymer contains at least 35 wt % fluorine. 
     
     
       8. The cross-linked fluoropolymer composition of  claim 1  wherein said functional groups are selected from the group consisting of ester, acid, salt and halide of said acid, epoxide, and anhydride. 
     
     
       9. The composition of  claim 8  wherein said anhydride is derived from maleic anhydride. 
     
     
       10. The fluoropolymer composition of  claim 8  wherein said functional groups are selected from the group consisting of ester, acid, salt and halide of said acid, epoxide, and anhydride. 
     
     
       11. The cross-linked fluoropolymer composition of  claim 1  wherein said fluoropolymer is selected from the group consisting of perfluorinated copolymer, copolymer of ethylene with tetrafluoroethylene or chlorotrifluorethylene, and vinylidene fluoride homopolymer and copolymer with perfluoroolefin, which has been functionalized or said functional groups are pendant from polymerized monomer present in said fluoropolymer, said monomer having the formula CF 2 ═CFRfX, wherein R f  is a fluorinated diradical and X is said functional groups. 
     
     
       12. The composition of  claim 2  wherein said fluoropolymer is selected from the group consisting of perfluorinated copolymer, copolymer of ethylene with tetrafluoroethylene or chlorotrifluorethylene, and vinylidene fluoride homopolymer and copolymer with perfluoroolefin which has been functionalized, or said functional groups are pendant from polymerized monomer in said fluoropolymer, said monomer having the formula CF 2 ═CFR f X, wherein R f  is a fluorinated diradical and X is said functional groups.